The Art of Apple Breeding at the University of Minnesota
Stroll through the apple offerings at your local farmer’s market or grocery store and you’ll likely spot fan favorites like Honeycrisp, Zestar and Haralson. For these varieties—and 25 others—we thank the University of Minnesota’s apple breeding program, which strives to develop superior apples by strategically making crosses between different varieties.
Releasing 28 new apple varieties over the course of the program’s 145-year history is no small feat, considering the process to introduce a single new variety to the market takes roughly 25 to 30 years. From DNA testing and hand-pollinating to taste testing and grafting, the apple breeding process is remarkably intricate and continues to evolve to meet a myriad of stakeholders’ needs.
Driven by Purpose
When the program was first established in the late 1800s, the goal was to produce apple varieties that could withstand the state’s harsh winters. While winter hardiness is still an important consideration, developing apples that deliver on texture, flavor and appearance is key today.
“We like to say that attractive skin helps make the first purchase, and then following purchases are going to depend on that eating experience—so it better be memorable,” says Jim Luby, a professor in the College of Food, Agricultural and Natural Sciences (CFANS) departments of horticultural science and director of the school’s fruit breeding program.
Luby identifies consumers as the “ultimate stakeholder” but is quick to point out several others, including growers, producers and retailers, for whom factors like reliable annual production, minimal pre-harvest dropping and diseases resistance are critical.
“We’d like to provide them with a variety that’s economically and maybe hopefully more environmentally sustainable for production,” Luby explains.
A Yearslong Process
If you’re at all familiar with how dating apps function, you already have a general, albeit overly simplistic, idea of how apple breeding works. As Luby puts it, “We’re a dating and mating service for apples.”
The first year: The apple breeding process starts with identifying crosses. Just as you might swipe left or right on an app to find a match, Luby and his team select varieties they think might produce a superior variety. These “parent” varieties are selected during the winter using DNA and performance data.
In the spring at the Horticultural Research Center in Victoria, Minnesota/ the team cross-pollinates the glowers by hand, collecting pollen from trees they’ve deemed the male parent and applying the pollen to the flowers of the female parents. A pager bag covers the flowers to help keep insects and other unwanted elements at bay.
The hybrid seeds then germinate in a greenhouse and a leaf from each plant is used for DNA test results. At this stage, a third to half of the seedlings are discarded.
Years 2-5: Plants that look promising move into bigger containers and head outside where the team performs a “horticultural trick.”
“We will take a little bit of steam from each of them, and graft it onto a rootstock that has been planted in the field this spring,” Luby says. “And that rootstock, it’s a dwarfing type of rootstock, so it makes a tree smaller and also brings it into fruiting earlier in its life.”
When the seedlings start to produce fruit, Luby and his team jump into action, taste-testing up to hundreds of apples each day.
Years 5-15: Those trees that move on for further evaluation are called “selections.” The selections are cloned via grafting onto two different rootstocks—a dwarfing and a semi dwarfing—and then planted in a more commercial-like environment.
“We want to make sure that the traits that we saw in the initial tree that was from the seedling, still hold true when you graft up a few copies of it,” Luby says.
Over the next 10-15 years, the team evaluates the selection on 25 tree and fruit characteristics, discarding most during the process.
Years 15-20: The best, most promising selections enter the final round of testing and are planted in commercial orchards across the state and country. Those selections that thrive in different environments and are of interest to growers move forward to the commercialization process.
Years 20-25: Selections are named, receive intellectual property protections, and are licensed and distributed to commercial growers.
Years 25-30: The fruit becomes available to consumers about five years after commercial growers begin propagating the trees.
Evaluating an Apple
Apples are evaluated on dozens of characteristics like size and storage ability, but top traits considered are texture, flavor and appearance. “Most important is the texture of the fruit” Luby emphasizes. “We want a fruit that is really crispy and crunchy and juicy.”
Like texture, the preference for appearance is consistent, with the U of M team looking for apples with smooth, bright skin. In addition to looking great from a consumer perspective, a smooth, crack-free skin helps the apple retain its moisture and keeps fungi away.
You, as a consumer, likely know that taste is far more varied.
“If I go in the room and I said, ‘Who likes a tart apple?’ Maybe half the hands will go up. ‘Who likes a sweet apple?’ And the other half of the hands will go up,” Luby says. “And then there’s some other flavors in apples that we can get spiciness or extra fruitiness or other characteristics.”
An Innovative History
The University of Minnesota’s apple breeding program is continually regarded as one of the best in the country and leans into horticultural and genetic advancements and innovation. One major update in the apple breeding process at the U of M was the decision to graft onto rootstock, which occurred in the late 1990s.
“The adoption of using the dwarfing rootstocks has been our biggest horticultural innovation that has probably sped up the breeding cycle maybe three or four years,” Luby says.
Within the past decade, DNA genetic testing became less expensive, allowing the team to make more informed decisions when identifying crosses and predict key traits, all with the goal of developing better apples for growers, producers, retailers and—most importantly—you.
Did you know?
- More than 2,500 apple varieties currently grow in the United States.
- The Crabapple is the only apple native to North America.
- Apples are part of the rose family, or rosaceae.
- The largest apple on record weighed in at just over 4 pounds.
- Roughly 30-40 apples are needed to produce a gallon of apple cider.